Immunohistochemical delineation of the conduction system. I: The sinoatrial node.

We have raised a mouse monoclonal antibody that reacts specifically with the myocytes of the sinoatrial node of the bovine heart. By use of this antibody (445-6E10) and antibodies against the gap junction protein connexin43, the periphery of the sinoatrial node and the distribution of gap junctions in the nodal region were studied. The reaction patterns of 445-6E10 and anti-connexin43 are exactly complementary; ie, connexin43 was not detected in the nodal myocytes but was clearly present in the atrial myocytes. Both reaction patterns demonstrate that nodal myocytes and atrial myocytes can unambiguously be distinguished by their characteristic molecular phenotype. The transitional nodal myocytes at the periphery of the node that have intermediate morphological and electrophysiological characteristics could now clearly be defined as nodal by our immunohistochemical criteria. The center of the node is surrounded by a region of interdigitating nodal and atrial bundles. Nodal bundles, coming from the center of the node, penetrate the atrial myocardium aligned at atrial bundles, forming histological connections between nodal and atrial myocytes at regular distances. This interdigitating arrangement of bundles of connexin43-negative nodal and connexin43-positive atrial myocytes is also found in the human and rat heart. We hypothesize that the architecture of the periphery of the node is important to prevent silencing of the pacemaking nodal myocytes by the atrium while ensuring a sufficient source loading of the nodal myocytes.

[1]  M Delmar,et al.  Gap junctional channels in adult mammalian sinus nodal cells. Immunolocalization and electrophysiology. , 1992, Circulation research.

[2]  A E Becker,et al.  Functional and Morphological Organization of the Rabbit Sinus Node , 1980, Circulation research.

[3]  H. A. Meyling,et al.  The conducting system of the heart in hoofed animals. , 1957, The Cornell veterinarian.

[4]  R. Zahler,et al.  The cardiac conduction system in the rat expresses the alpha 2 and alpha 3 isoforms of the Na+,K(+)-ATPase. , 1992, Proceedings of the National Academy of Sciences of the United States of America.

[5]  G. Köhler,et al.  A better cell line for making hybridomas secreting specific antibodies , 1978, Nature.

[6]  Y. Yazaki,et al.  Distribution of cardiac myosin isozymes in human conduction system. Immunohistochemical study using monoclonal antibodies. , 1984, The Journal of clinical investigation.

[7]  M. Taylor,et al.  Reconstruction of the human sinoatrial node , 1967, The Anatomical record.

[8]  V. Lehto,et al.  A comparative analysis of intermediate filament proteins in bovine heart Purkinje fibres and gastric smooth muscle. , 1987, European journal of cell biology.

[9]  M. Halpern.  The sino‐atrial node of the rat heart , 1955, The Anatomical record.

[10]  Y. Yazaki,et al.  Isolation and Characterization of Myosin Heavy Chain Isozymes of the Bovine Conduction System , 1987, Circulation research.

[11]  A. Moorman,et al.  Spatial distribution of “tissue‐specific” antigens in the developing human heart and skeletal muscle. I. An immunohistochemical analysis of creatine kinase isoenzyme expression patterns , 1990, The Anatomical record.

[12]  A Keith,et al.  The Form and Nature of the Muscular Connections between the Primary Divisions of the Vertebrate Heart. , 1907, Journal of anatomy and physiology.

[13]  L. Thornell,et al.  Isolation and partial characterization of intermediate filament protein (skeletin) from cow heart Purkinje fibres. , 1979, Biochimica et biophysica acta.

[14]  L. Christensen,et al.  Universal Immunoperoxidase Staining Protocol to Optimize the Use of Polyclonal and Monoclonal Antibodies , 1987 .

[15]  T Opthof,et al.  Functional morphology of the mammalian sinuatrial node. , 1987, European heart journal.

[16]  W H Lamers,et al.  Spatial distribution of “Tissue‐Specific” antigens in the developing human heart and skeletal muscle. II. An immunohistochemical analysis of myosin heavy chain isoform expression patterns in the embryonic heart , 1991, The Anatomical record.

[17]  D. Gros,et al.  The Plasma Membrane of Leading Pacemaker Cells in the Rabbit Sinus Node: A Qualitative and Quantitative Ultrastructural Analysis , 1979, Circulation research.

[18]  D. Scheidegger,et al.  Production of monoclonal antibodies: strategy and tactics. , 1980, Journal of immunological methods.

[19]  A. Moorman,et al.  Immunohistochemical distribution of the histone H1(0)/H5 variant in various tissues of adult Xenopus laevis. , 1985, Cell differentiation.

[20]  J. Hoh,et al.  Electrophoretic analysis of multiple forms of myosin in fast-twitch and slow-twitch muscles of the chick. , 1976, The Biochemical journal.

[21]  W H Lamers,et al.  Immunohistochemical delineation of the conduction system. II: The atrioventricular node and Purkinje fibers. , 1993, Circulation research.

[22]  W H Lamers,et al.  Spatial distribution of connexin43, the major cardiac gap junction protein, in the developing and adult rat heart. , 1991, Circulation research.

[23]  N. Severs.  The cardiac gap junction and intercalated disc. , 1990, International journal of cardiology.

[24]  J. Saffitz,et al.  Cardiac myocytes express multiple gap junction proteins. , 1992, Circulation research.

[25]  H. Jongsma,et al.  Pacemaker cell types in the rabbit sinus node: a correlative ultrastructural and electrophysiological study. , 1984, Journal of molecular and cellular cardiology.

[26]  G. Morris,et al.  Monoclonal-antibody studies of creatine kinase. The proteinase K-cleavage site. , 1985, The Biochemical journal.

[27]  A. Moorman,et al.  Isomyosin expression patterns during rat heart morphogenesis: An immunohistochemical study , 1989, The Anatomical record.

[28]  S. Virágh,et al.  THE IMPULSE GENERATION AND CONDUCTION SYSTEM OF THE HEART , 1973 .

[29]  F. V. Van Capelle,et al.  Propagation through electrically coupled cells. How a small SA node drives a large atrium. , 1986, Biophysical journal.

[30]  H. Towbin,et al.  Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications. , 1979, Proceedings of the National Academy of Sciences of the United States of America.

[31]  U. K. Laemmli,et al.  Cleavage of structural proteins during , 1970 .

[32]  J. Léger,et al.  Developmental Changes in the Human Cardiac Isomyosin Distribution: An Immunohistochemical Study Using Monoclonal Antibodies , 1987 .

[33]  J. Freund,et al.  Sensitization to Horse Serum by Means of Adjuvants , 1942 .

[34]  S. Schiaffino,et al.  Myosin types and fiber types in cardiac muscle. III. Nodal conduction tissue , 1986, The Journal of cell biology.

[35]  L. Barr,et al.  Propagation of Action Potentials and the Structure of the Nexus in Cardiac Muscle , 1965, The Journal of general physiology.

[36]  T. N. James,et al.  Anatomy of the sinus node, AV node and os cordis of the beef heart , 1965, The Anatomical record.

[37]  L. Thornell,et al.  Monoclonal antibody to desmin purified from cow Purkinje fibers reveals a cell‐type specific determinant , 1990, FEBS letters.

[38]  H. Jongsma,et al.  Structure and function of the sino-atrial node: a review. , 1986, European heart journal.